Electronic system to control operator circuits as a function of speed of machine rotating member

ABSTRACT

An electronic engine r.p.m. limiter for use with an electronic ignition system controlled by a magnetic pulser generating pulses having a frequency proportional to the engine speed. An amplifier-waveshaper at the input of the limiter device supplies a control signal both to the electronic ignition circuit and to the remainder of the limiter device. This remainder converts the incoming pulse signals to a D.C. signal varying in accordance with the engine speed and compares this variable D.C. signal with a fixed D.C. (threshold) signal. When the variable D.C. signal exceeds the fixed threshold, an actuator circuit becomes operative to short-circuit the control signals for the electronic ignition, thereby cutting off the operation thereof until the engine speed is below a predetermined maximum limit.

United States Patent 1191 Vignozzi et al.

[451 Aug. 19, 1975 [75] Inventors: Pietro Vignozzi, Rome; Paolo Cerioli, Bologna, both of Italy [73] Assignee: Fabbrica Italiana Magneti Marelli S.p.A., Milan, Italy [22] Filed: Mar. 28, 1973 [21] Appl. No.: 345,675

[30] Foreign Application Priority Data 3,695,242 10/1972 Fada et al. 123/102 3,703,887 l1/1972 Panhard 123/117 R 3,738,339 6/1973 Huntzinger et al.... 123/148 E X 3,776,204 12/1973 Harris 123/102 Primary ExaminerCharles J. Myhre Assistant Examiner-Joseph A. Cangelosi Attorney, Agent, or F irmOstro1enk, Faber, Gerb & Soffen [57] ABSTRACT An electronic engine r.p.m. limiter for use with an electronic ignition system controlled by a magnetic pulser generating pulses having a frequency propor- Mar. 28, 1972 Italy 22461/72 tionai to the engine speed An ampiifier waveshaper at the input of the limiter device supplies a control signal [52] CL 123/102; 123/117 R; 123/32 EA both to the electronic ignition circuit and to the re- [51] Int. Cl. F02p l l/OO mainder of the miter device i remainder converts [58] Field of Search 123/148 E, 117 R, 102 the incoming pulse Signals to a DC signal Varying in accordance with the engine speed and compares this 1 References Cited variable DC. signal with a fixed D.C. (threshold) sig- UNITED STATES PATENTS nal. When the variable DC. signal exceeds the fixed 3,434,462 3/1969 Schneider et a1. 123/148 E threshold, an actuator Circuit becomes Operative to 3.563,.219 2/1971 Mieras 123/148 E short-circuit the control signals for the electronic igni- 3,581,720 6/1971 H mp 23/148 E tion, thereby cutting off the operation thereof until the 3,582,679 6/1971 Cays et a1. 123/102 engine speed is below a predetermined maximum 3,636,933 1 1972 Ohtani et a1. 123 102 limit. 3,651,793 3/1972 Roth et a1. .1 123/102 3,660,689 5/1972 Oishi et a1. 123/148 E X 15 Claims, 5 Drawing Figures zzirr/e'a/v/c ENG/1V5 SPEED //V0/C'/7 70 1 /A9" F 6Q/A/QE WAVE ACTH/l 7025 K Z 1 c0/1/ML QTER 4 I 5; 7

/A/7ff/YA70 i 74/ 1 WA 1/5 WFM/A/Q H -l fl/WPA/HE/P 1 5'2 72 i1 l-- --l l 1. 1

ELECTRONIC SYSTEM TO CONTROL OPERATOR CIRCUITS AS A FUNCTION OF SPEED OF MACHINE ROTATING MEMBER This invention relates to an electronic apparatus for controlling operating circuits according to the revolving speed of a member associated with a machine, this member rotating at a varying speed as the operating speed of the machine varies.

It is a general object of the invention to provide an apparatus of the above character and capable of energizing special operating circuits or devices, forming or not forming a part of the machine, only when the rotating member reaches a predetermined r.p.m.

It is a specific object of the invention to provide an apparatus for controlling the ignition in motor-vehicle engines, capable of operating as a limiting device for the engine r.p.m. and/or as advance switch.

A further object of the invention is to provide an apparatus for detecting the speed of the rotating member.

According to the invention, the above, as well as other objects are accomplished by an apparatus comprising in combination: means for sensing the revolving speed, cooperating with the rotating member and either directly or through wave forming means capable of providing square wave signals at a constant average value and variable frequency as the speed of said member varies; a converter for receiving said constant average value signals and converting such signals to square wave signals of the same frequency, but variable average value; an integrator for receiving said average value signals of a variable nature and converting such signals to a continuous signal linearly varying according to frequency; comparing means for comparing said variable continuous signal with one or more reference signals (threshold signals) corresponding to specific r.p.m. of the machine (or of the rotating member) and providing control signals as soon as the variable signal exceeds said reference signals; control or actuating means for acting on the operating circuits, and forming or not forming a part of the machine, when energized by the control signals of said comparing means; and in such case, means for detecting the speed of the rotating member, which means is connected to the output from the integrator.

In the application of the apparatus to motor-vehicles, the square wave signals from the sensing means, either directly or through the wave forming means, are provided both to the converter and to the ignition control circuit, and the comparator is preset to become effective at the maximum or predetermined r.p.m. of the engine depending on the apparatus to operate as an r.p.m. limiting device, or as an advance switch.

In order to overcome the disadvantages due to ignition disturbing signals or battery voltage changes, the apparatus could be also provided with antidisturbing and supply voltage smoothing circuits.

Further features and advantages of the invention will become more apparent from the following description in connection with the accompanying drawings, in which:

FIG. I is a general block diagram for the electronic apparatus using an electronic pulser;

FIG. 2 is a block diagram for the apparatus when used as a limiting device for r.p.m. of an internal combustion engine in motor-vehicles;

FIG. 3 is a block diagram for the apparatus when used both as a limiting device for r.p.m. and as advance switch of an internal combustion engine in motor vehicles;

FIG. 4 is a modified embodiment of the block diagram shown in FIG. 3; and

FIG. 5 is an embodiment of the block diagram shown in FIG. 2.

Referring to FIG. 1, it will seen that the apparatus therein schematically shown comprises; a rotating member R associated with a machine, not shown, the r.p.m. of which varies as the r.p.m. of the machine van'es; a revolving speed sensor 1 coupled to said member R and capable of providing, as the latter rotates, pulses of which the frequency varies as the speed of said member R varies; a wave forming amplifier 2, hereinafter simply referred to as wave forming means, which is coupled to the sensor and capable of converting the pulse signals from sensor 1 to constant average value square wave signals of the same frequency; a converter 3 for converting the signals from said wave forming means 2 to square wave signals of a varying average value, but of the same frequency; an integrator 4 supplied by the signals from converter 3 and providing a continuous signal varying linearly with the frequency, so that at its output 5 a continuous signal is available, the level of this signal varying as the r.p.m. of the rotating member I or the machine varies; comparators 6, 6a, 6b, etc. connected to the integrator, each being capable of comparing the signal at output 5 with a proper predetermined reference or threshold signal corresponding to'a given r.p.m. of said member R, so that one or more comparators are concurrently energized when the level of signal at output 5 is the same as or exceeds that of the reference signals; and control or actuating devices 7, 7a, 7b, etc. connected to the comparators and being effective on given operating circuits, when energized by said comparators, there being also provided a device 18 for using the signal at output 5 for different purposes.

The term machine as herein used is to mean any machine, motor or engine, device, etc., the r.p.m. of which can be represented by a rotating member.

The term comparator energization is intended herein to mean the operating condition, whereby a signal is available at its output sufficient to energize the corresponding control or actuating device or devices.

The operation of these devices on the operating circuits, which may or not be a part of the machine, can be effected in different ways, such as by energization, de-energization or switching of circuits.

In FIGS. 2-5, relating to the application of the apparatus to a motor-vehicle for engine ignition control, the corresponding parts are designated by the same reference characters, but followed by a prime In such an application (see FIG. 2), the rotating member may comprise a gear wheel (phonic wheel) R, driven by the engine shaft or by the camshaft and the revolving speed sensor coupled thereto by a magnetic pick-up 1'. As readily understood, the assembly of the gear wheel R, pick-up 1' and wave forming means 2 comprises an electronic contact breaker.

Moreover, to overcome the disadvantages due to disturbing signals and motor-vehicle battery voltage changes, the apparatus can be completed with the addition of an antidisturbing attenuator 8, as connected between said wave forming means 2' and converter 3, and

a voltage regulator 9 for said converter and comparators. v

In order to control the engine ignition, in addition to its normal output 10 said wave forming means 2 also has a second output 11 supplying the square wave sig nal to the ignition control circuit 12.

In FIG. 2, particularly relating to the use of the apparatus as a r.p.m. limiting device, the output 11 is directly connected to the circuit 12 by means of a line 13. Furthermore, the comparator 6 is set with a reference signal (or threshold signal) corresponding to the predetermined maximum r.p.m. of the engine, and the control device 7, which can comprise an electronic switch, is effective on circuit12.

As the engine, and hence the wheel R, speed increases, and when the signal at output 5 is equal to or exceeds the reference signal of the comparator 6, the latter is energized, and as a result the device 7 is energized for cutting off, or otherwise rendering inoperative the control signal of circuit 12 from said second outpu 11. As the ignition is cut off, the engine rpm. is reduced and when the signal at output 5 drops to a value below the reference value of the comparator 6, the latter returns to its inoperative or rest condition, the device 7 is de-energized and, as a result, the connection between the output 11 of the forming wave means 2 and the ignition control circuit 12 is reestablished.

In FIG. 3, relating to the use of the apparatus also as an advance switch, in addition to the components shown in FIG. 2, provision is also made for a second sensor 1" which is out of phase by an angle 6 relative to sensor 1', a second wave forming means 14, similar to said wave forming means 2, but provided with a single output 15,'whereat the square wave signal is also present, a second comparator 6a also stabilized by said voltage regulator 9, and a second control device or actuator 7a, controlled by comparator 6a and connected in the supply line of circuit 12. Comparator 6a is set by a reference signal corresponding to the engine attained r.p.m., whereby the advance must be switched, and the device 7a comprises an electronic switch, as schematically shown.

In the drawing; the switch is a two-way type of switch, having a first position for connecting the line 13 from output 11 to the control circuit 12, and a second position, controlled by the energization of comparator 6a, for connecting the line 16 from output 5 to said control circuit 12.

In the case of further advances, it is apparent that the apparatus may comprise further sensors, wave forming means and comparators, and the electronic switch will be of a suitable design to effect the further connections, when energized by the associated comparator set for the reference signal corresponding to the given engine r.p.m., of which the further advance is desired.

According to the modified embodiment of FIG. 4, showing a simplified form of the apparatus of FIG. 3, the advance switching is provided in a much more economical manner by using for all of the required advances the same and single wave forming means 2, already provided for the general operation of the apparatus. On the contrary, there are still required a proper sensor and comparator and a suitable electronic switch for each of the further advances. I

The removal of the further wave forming means can be provided by an advance switching device positioned downstream rather than upstream of the wave forming means 2'.

Thus, referring to FIG. 4, it will be seen that switch 7a, still controlled by comparator 6a, provides for switching said sensors 1' and 1 on the input to the wave forming means 2', whereas the output 11 of the latter is directly connected to circuit 12, as in the case of FIG. 2.

When a second advance is desired, there will be required a third sensor, and a third comparator, as well as a suitable switch also controlled by the third comparator.

Of course, the apparatus of FIG. 3 and FIG. 4 could be simply used as advance switches, in this case dispensing with the comparator 6 and device 7 functioning to limit the engine r.p.m.

Still referring to the application to motor-vehicles, the apparatus could also be provided for cutting off at high engine rates, the operation of other devices, such as the exhaust gas postcombustion pump. For such a cut off, a control device could be effective, such as control device 7b (see FIG. 1) controlled by a comparator, such as 6b, which is set to operate as soon as the engine reaches the predetermined rpm, to which such an engine device as the pump is to be cut off.

Finally, the apparatus provides for detection of engine speed. To this end, it will suffice to connect an electronic tachometer to the integrator output 5, as shown for device 18 (see FIG. 1).

The circuit shown in FIG. 5 will now be described.

The wave forming means 2', also operating as an amplifier, comprises two transistors 21 and 22. The base of the output transistor 21 is connected through a decoupling diode 23 to sensor 1 and its collector is connected through a resistor 24 to the base of the final transistor 22 and the antidisturbing attenuator circuit 8. The collector 11 of transistor 22 is connected both to the base of transistor 21 by means of a reactive resistor 25 and to the ignition control circuit 12 by means of the line 13. The diode 26 and resistor 27 function to shield and bias the base of transistor 21, respectively.

The resistors 28 and 29 are the load resistors for transistors 21 and 22, respectively, and additionally said resistor 28, is connected to battery 8+, and functions to bias the base of transistor 22. For the purpose of understanding the operation of transistor 22, the load resistor 29 (see the dashed lines) has been shown as connected in the circuit of the wave forming means 2', but as a matter of fact said resistor is a part of the ignition control circuit 12.

During the rotation of member R, at the outputs 10 and 11 of the transistors 21 and 22 respectively there will appear square wave signals of a constant average value but of a frequency varying as the speed of member R' varies.

The antidisturbing attenuator 8 comprises the voltage divider 81 82 on the collector output 83 of transistor 84 and the disturbance suppressor comprising a capacitor 85 acting as a filter, and a Zener diode 86. The divider output 87, to which said suppressor is connected, is connected by means of a resistor 88 to the converter 3.

The base of transistor 84, which is connected by with resistor 24 with to the output 10 of transistor 21, functions to amplify the signal on the collector of transistor 21 and to repeat the signal available at the output 11 of transistor 22.

Its collector 83 is connected through a load resistor 89 to battern B+.

The converter 3, having the square wave signal of a constant average value from the disturbance suppressor applied thereto, is provided with a monostable multivibrator comprising two transistors 31 and 32 having their collectors connected to battery B+ through the associated load resistors 33, 34 and the voltage regulator 9, and coupled by means of a regenerative RC network and a dual coupling network.

Said regenerative RC network comprises a capacitor 35 and a variable resistor 36, and the dual coupling (emitter-collector reaction) is provided by means of resistors 37 and 38.

Variable resistor 36 varies the duration of the pulses at output 39, such pulses being of square wave character, but the average value of which varies as the r.p.m. of member R varies. The emitter collector reaction or feedback serves the purpose of increasing the reliability of the multivibrator against disturbance signals, particularly those due to ignition.

The multivibrator output 39 is connected to the integrator 4 comprising a resistor 41 and a capacitor 42 forming an integrating cell.

The comparator 6 is provided by means of an operational amplifier 61 of the open ring connected type.

With its negative input, this amplifier is connected through a resistor 62 to the common terminal of resistive divider 63, 64, the latter negative input being sup plied by battern B+ through the voltage divider 9, and the positive input being connected through a resistor 65 to the output 5 of integrator 4, providing a continuous signal, the level of which varies as the speed of the rotating member R varies. The divider 63, 64 establishes the amplifier reference signal or threshold signal. When the apparatus operates as an r.p.m. limiting device, this signal will correspond to the predetermined maximum r.p.m. When this rate is attained, the operational amplifier 61 will operate to energize the control device 7, being connected through a resistor 66 thereto.

The engine r.p.m., at which said operational amplifier 61 is to be switched, can be adjusted by adjusting the variable resistor 36 of the multivibrator. Alternatively, the adjustment could be accomplished by adjusting the voltage divider 63, 64.

The device 7, comprising the apparatus attenuator, is provided by means of an electronic switch including two cascade-connected transistors 71 and 72. The collector of the input transistor 71 is connected through a load resistor 73 to battery B+, and the collector of the switch output transistor 72 is connected to the output from the amplifier output transistor 22 of the wave forming means 2.

When, operational amplifier 61 is energized, a control signal is supplied to transistor 71, causing transistors 71 and 72 to become conductive, with the result that the output 11 of the wave forming means 2 is to ground and the control signal to circuit 12 is cut off.

Finally, the voltage regulator 9, supplying both the monostable multivibrator 3 and operational amplifier 61, comprises a current generator formed of diodes 91 and 92 and transistor 93 having emitter and base resistances 94 and 95, and a Zener diode 96 functioning to smooth down the voltage.

In the preceding embodiment (see FIGS. 1 to 5), reference was made to an apparatus using an electronic pulser comprising a sensor and a wave forming means for always providing a speed signal to converter 3. However, it is apparent that the foregoing still applies if the pulser is of a mechanical type, such as a hammer breaker, mounted on the camshaft or engine shaft.

Of course, in such a case the wave forming means is no more required, since it is the breaker itself, now coincident with the sensor, to provide the square wave signals, that is in the form advantageous for the subsequent processings in the apparatus and controlling the circuit 12 of FIGS. 2 and 4.

By using a mechanical breaker, the apparatus of FIG. 2 would not require the wave forming means or block 2, and the coincident points or outputs 10 and 11 would be directly supplied by the breaker hammer, which can be shown at 1. In this case, it is apparent that in order to have always a speed signal at the input to the attenuator 8 or converter 3, it would be required to connect a separator on line 13. This separator could also form part of circuit 12 and in a more advantageous embodiment it could comprise a circuit, such as a monostable multivibrator, already provided in circuit 12 for other purposes.

Similarly, for the advance switching operational mode, the block 2 in the apparatus of FIG. 4 can be dispensed with and the coincident points 10 and 11 would be supplied by hammer 1' or 1 depending on the position of switch 7a.

What is claimed is:

1. An electronic apparatus for controlling at least one operating circuit according to the revolving speed in r.p.m. of a rotating member coupled to a machine, said rotating member being rotated at a speed which varies as a rotational speed in r.p.m. of the machine varies, characterized by comprising in combination: pulsing means, cooperating with the rotating member, for providing square wave signals at first and second outputs, said signals having a constant average value and a frequency which varies as the revolving speed of said rotating member varies; converter means for receiving said signals from one of said first and second outputs, which signals have a constant average value and converting said signals to square wave signals having the same frequency, but variable average value; integrator means for receiving said signals having a variable average value from said converter and converting these signals to a continuous signal which varies linearly with the frequency of the converter output signal; at least one comparator means for comparing said variable continuous signal from said integrator with at least one reference (threshold) signal having a value equal to a signal from said integrator corresponding to a given r.p.m. of the machine (or given r.p.m. of the rotating member), each of said comparator means adapted to provide a control signal at an output thereof when the variable signal exceeds the reference signal associated with that comparator means; control means for acting on each of the operating circuits when energized by at least one of the control signal outputs of the comparator means; said control means being adapted to shortcircuit the remaining of the first and second outputs of said pulsing means coupled to one of said operating circuits.

2. An apparatus as claimed in claim 1, characterized in that said pulsing means comprises electronic sensor means for sensing the revolving speed of the rotating member, to provide pulses of a frequency that vary with the revolving speed of said member and electronic wave forming means for receiving and converting said pulses to square wave signals having a constant average value at the same frequency.

3. An apparatus as claimed in claim 2, characterized in that said electronic wave forming means (2') comprise at least one input transistor and one amplifier output transistor connectd by means of a feedback network, the outputs of which respectively supply the control signal to said converter and an ignition control circuit.

4. An apparatus as claimed in claim 2, characterized in that said converter includes a monostable multivibrator comprising at least one input transistor and one output transistor, the emitter and collector being simultaneously coupled.

5. An apparatus as claimed in claim 4, characterized in that the triggering of the operational amplifier is varied by providing an adjustable resistor in regenerative loop of the monostable multivibrator, whereby the adjustment thereof adjusts the triggering of the operational amplifier.

6. An apparatus as claimed in claim 2 characterized in that each comparator comprises an operational amplifier having first and second inputs, the first input of which is connected to the integrator output, the second input of said operational amplifier being connected to a voltage divider for setting the reference signal.

7. An apparatus as claimed in claim 6, characterized in that the triggering of the operational amplifier is varied by adjusting the voltage divider.

8. An apparatus as claimed in claim 2, characterized in that said control means comprises at least one input transistor coupled to said comparator means and one switch transistor coupled to said pilot transistor and the output of said pulsing means, the conducting condition of said switch output transistor occurring as soon as the operational amplifier applies a control signal to the input transistor, to short circuit the output of the pulsing means.

9. An apparatus as claimed in claim 2, characterized by comprising a voltage regulator for supplying the converter and comparators, and an antidisturbing attenuator connected between the converter and the pulsing means.

10. An apparatus as claimed in claim 9, characterized in that said anti-disturbing attenuator comprises an amplifier transistor; and an anti-disturbance attenuator circuit comprising a voltage divider, a capacitor parallel connected to a first Zener diode, the cathode of which is connected to an intermediate point of the voltage divider, and the anode of which is grounded.

1 1. An apparatus as claimed in claim 9, characterized in that said voltage regulator comprises; a DC. generator including atransistor, the base of which is biased by means of diodes, and a resistor; and, a Zener diode biased by said D.C. generator.

12. An apparatus as claimed in claim 1, applied to a motor-vehicle as a limiting device to the engine r.p.m., characterized by comprising: a sensor cooperating with a member rotatably driven by the engine shaft or cam shaft; one operating circuit comprising an ignition control circuit; said pulsing means Comprising a wave forming means providing the square wave signal appearing at said first and second outputs both to the converter and the ignition control circuit; the comparator reference signal having a value equal to a signal from said integrator corresponding to the predetermined maximum r.p.m. for the engine; said control means rendering inoperative the signal supplied from the wave forming means to the ignition control circuit as soon as energized by the comparator.

13. An apparatus as claimed in claim 1, characterized in that said pulsing means are of a mechanical type and comprise a hammer breaker associated with the rotating member, so as to provide at its output square wave signals having a constant average value and a frequency that varies as the revolving speed of said rotating member varies.

14. An apparatus as claimed in claim 1, applied to a motor-vehicle as a limiting device for the engine r.p.m., characterized by comprising: a breaker carried on the cam shaft and supplying the square wave signal both to the converter and ignition control circuit; a comparator, the reference signal of which has a value equal to a signal from said integrator, which value corresponds to the predetermined maximum r.p.m.; control means for rendering inoperative the signal being supplied by the breaker to the ignition control circuit, as soon as energized by the comparator.

15. Electronic speed limiting apparatus for limiting the operating speed of a machine having a rotating member whose speed varies as a rotational speed in r.p.m. of the machine varies, said apparatus comprising:

means for electromagnetically sensing the speed of the rotating member to generate an output signal representative of the r.p.m. of the rotating member; pulsing means coupled to said sensing means for generating square pulses having a constant average value and a frequency which varies in accordance with the r.p.m. of the rotating member, said pulsing means comprising an input transistor and an output transistor for providing a first square wave output of constant average value on the collector of said input transistor and a second square wave output of constant average value on the collector of said second transistor; converter means receiving said first square wave outputs for converting the signal to square wave signals having an average value variable ,with frequency (or engine r.p.m.);

means for integrating the output of said converter means to thereby generate a variable DC. signal which varies linearly with the frequency of the output signal of said converter means; means for providing a constant reference level corresponding to a given r.p.m. of the machine;

comparator means for comparing the output of said integrating means against said reference level for generating control signals when the magnitude of the integrating means output exceeds the reference level; and

control means coupled to said comparator means for short-circuiting the remaining one of the pulsing means first and second outputs in the presence of a control signal to prevent the output of the pulsing means from increasing the r.p.m. of the machine. 

1. An electronic apparatus for controlling at least one operating circuit according to the revolving speed in r.p.m. of a rotating member coupled to a machine, said rotating member being rotated at a speed which varies as a rotational speed in r.p.m. of the machine varies, characterized by comprising in combination: pulsing means, cooperating with the rotating member, for providing square wave signals at first and second outputs, said signals having a constant average value and a frequency which varies as the revolving speed of said rotating member varies; converter means for receiving said signals from one of said first and second outputs, which signals have a constant average value and converting said signals to square wave signals having the same frequency, but variable average value; integrator means for receiving said signals having a variable average value from said converter and converting these signals to a continuous signal which varies linearly with the frequency of the converter output signal; at least one comparator means for comparing said variable continuous signal from said integrator with at least one reference (threshold) signal having a value equal to a signal from said integrator corresponding to a given r.p.m. of the machine (or given r.p.m. of the rotating member), each of said comparator means adapted to provide a control signal at an output thereof when the variable signal exceeds the reference signal associated with that comparator means; control means for acting on each of the operating circuits when energized by at least one of the control signal outputs of the comparator means; said control means being adapted to short-circuit the remaining of the first and second outputs of said pulsing means coupled to one of said operating circuits.
 2. An apparatus as claimed in claim 1, characterized in that said pulsing means comprises electronic sensor means for sensing the revolving speed of the rotating member, to provide pulses of a frequency that vary with the revolving speed of said member and electronic wave forming means for receiving and converting said pulses to square wave signals having a constant average value at the same frequency.
 3. An apparatus as claimed in claim 2, characterized in that said electronic wave forming means (2'') comprise at least one input transistor and one amplifier output transistor connectd by means of a feedback network, the outputs of which respectively supply the control signal to said converter and an ignition control circuit.
 4. An apparatus as claimed in claim 2, characterized in that said converter includes a monostable multivibrator comprising at least one input transistor and one output transistor, the emitter and collector being simultaneously coupled.
 5. An apparatus as claimed in claim 4, characterized in that the triggering of the operational amplifier is varied by providing an adjustable resistor in regenerative loop of the monostable multivibrator, whereby the adjustment thereof adjusts the triggering of the operational amplifier.
 6. An apparatus as claimed in claim 2 characterized in that each comparator comprises an operational amplifier having first and second inputs, the first input of which is connected to the integrator output, the second input of said operational amplifier being connected to a voltage divider for setting the reference signal.
 7. An apparatus as claimed in claim 6, characterized in that the triggering of the operational amplifier is varied by adjusting the voltage divider.
 8. An apparatus as claimed in claim 2, characterized in that said control means comprises at least one input transistor coupled to said comparator means and one switch transistor coupled to said pilot transistor and the output of said puLsing means, the conducting condition of said switch output transistor occurring as soon as the operational amplifier applies a control signal to the input transistor, to short circuit the output of the pulsing means.
 9. An apparatus as claimed in claim 2, characterized by comprising a voltage regulator for supplying the converter and comparators, and an antidisturbing attenuator connected between the converter and the pulsing means.
 10. An apparatus as claimed in claim 9, characterized in that said anti-disturbing attenuator comprises an amplifier transistor; and an anti-disturbance attenuator circuit comprising a voltage divider, a capacitor parallel connected to a first Zener diode, the cathode of which is connected to an intermediate point of the voltage divider, and the anode of which is grounded.
 11. An apparatus as claimed in claim 9, characterized in that said voltage regulator comprises; a D.C. generator including atransistor, the base of which is biased by means of diodes, and a resistor; and, a Zener diode biased by said D.C. generator.
 12. An apparatus as claimed in claim 1, applied to a motor-vehicle as a limiting device to the engine r.p.m., characterized by comprising: a sensor cooperating with a member rotatably driven by the engine shaft or cam shaft; one operating circuit comprising an ignition control circuit; said pulsing means comprising a wave forming means providing the square wave signal appearing at said first and second outputs both to the converter and the ignition control circuit; the comparator reference signal having a value equal to a signal from said integrator corresponding to the predetermined maximum r.p.m. for the engine; said control means rendering inoperative the signal supplied from the wave forming means to the ignition control circuit as soon as energized by the comparator.
 13. An apparatus as claimed in claim 1, characterized in that said pulsing means are of a mechanical type and comprise a hammer breaker associated with the rotating member, so as to provide at its output square wave signals having a constant average value and a frequency that varies as the revolving speed of said rotating member varies.
 14. An apparatus as claimed in claim 1, applied to a motor-vehicle as a limiting device for the engine r.p.m., characterized by comprising: a breaker carried on the cam shaft and supplying the square wave signal both to the converter and ignition control circuit; a comparator, the reference signal of which has a value equal to a signal from said integrator, which value corresponds to the predetermined maximum r.p.m.; control means for rendering inoperative the signal being supplied by the breaker to the ignition control circuit, as soon as energized by the comparator.
 15. Electronic speed limiting apparatus for limiting the operating speed of a machine having a rotating member whose speed varies as a rotational speed in r.p.m. of the machine varies, said apparatus comprising: means for electromagnetically sensing the speed of the rotating member to generate an output signal representative of the r.p.m. of the rotating member; pulsing means coupled to said sensing means for generating square pulses having a constant average value and a frequency which varies in accordance with the r.p.m. of the rotating member, said pulsing means comprising an input transistor and an output transistor for providing a first square wave output of constant average value on the collector of said input transistor and a second square wave output of constant average value on the collector of said second transistor; converter means receiving said first square wave outputs for converting the signal to square wave signals having an average value variable with frequency (or engine r.p.m.); means for integrating the output of said converter means to thereby generate a variable D.C. signal which varies linearly with the frequency of the output signal of said converter means; means for providinG a constant reference level corresponding to a given r.p.m. of the machine; comparator means for comparing the output of said integrating means against said reference level for generating control signals when the magnitude of the integrating means output exceeds the reference level; and control means coupled to said comparator means for short-circuiting the remaining one of the pulsing means first and second outputs in the presence of a control signal to prevent the output of the pulsing means from increasing the r.p.m. of the machine. 